Nutrition: What is it and why is it important?

Nutrition, nourishment, or aliment, is the supply of materials - food - required by organisms and cells to stay alive. In science and human medicine, nutrition is the science or practice of consuming and utilizing foods.

In hospitals, nutrition may refer to the food requirements of patients, including nutritional solutions delivered via an IV (intravenous) or IG (intragastric) tube.

Nutritional science studies how the body breaks food down (catabolism) and how it repairs and creates cells and tissue (anabolism). Catabolism and anabolism combined can also be referred to as metabolism. Nutritional science also examines how the body responds to food.

Fast facts on nutrition

The human body requires seven major types of nutrients.

Not all nutrients provide energy but are still important, such as water and fiber.

What is nutrition?

As molecular biology, biochemistry, and genetics advance, nutrition has become more focused on metabolism and metabolic pathways - biochemical steps through which substances inside us are transformed from one form to another.

Nutrition also focuses on how diseases, conditions, and problems can be prevented or reduced with a healthy diet.

Similarly, nutrition involves identifying how certain diseases and conditions may be caused by dietary factors, such as poor diet (malnutrition), food allergies, and food intolerances.

Dietitian vs. nutritionist

A registered dietitian nutritionist (RD or RDN) studies food, nutrition, and dietetics through an accredited university and approved curriculum, then completes a rigorous internship and passes a licensure exam to become a registered dietitian.

A nutritionist (without the title of an RD or RDN) studies nutrition via self-study or through formal education but does not meet the requirements to use the titles RD or RDN. The two terms are often interchangeable, but they are not identical.

Dietetics

Dietetics is the interpretation and communication of the science of nutrition; it helps people make informed and practical choices about food and lifestyle in both health and disease.

Part of a dietician's course includes both hospital and community settings. Dietitians work in a variety of areas, from private practice to healthcare, education, corporate wellness, and research, while a much smaller proportion work in the food industry.

A dietitian must have a recognized degree or postgraduate degree in nutrition and dietetics and meet continuing education requirements to work as a dietitian.

Nutrition

Nutritionists sometimes carry out research for food manufacturers.

Nutrition is the study of nutrients in food, how the body uses nutrients, and the relationship between diet, health, and disease.

Major food manufacturers employ nutritionists and food scientists.

Nutritionists may also work in journalism, education, and research. Many nutritionists work in the field of food science and technology.

There is a lot of overlap between what nutritionists and dietitians do and study. Some nutritionists work in a healthcare setting, some dietitians work in the food industry, but a higher percentage of nutritionists work in the food industry and in food science and technology, and a higher percentage of dietitians work in healthcare, corporate wellness, research, and education.

Types

A nutrient is a source of nourishment, a component of food, for instance, protein, carbohydrate, fat, vitamin, mineral, fiber, and water.

Macronutrients are nutrients we need in relatively large quantities.

Micronutrients are nutrients we need in relatively small quantities.

Macronutrients can be further split into energy macronutrients (that provide energy), and macronutrients that do not provide energy.

Nutritionally, polysaccharides are favored over monosaccharides because they are more complex and therefore take longer to break down and be absorbed into the bloodstream; this means that they do not cause major spikes in blood sugar levels, which are linked to heart and vascular diseases.

Proteins - 4 kcal per gram

There are 20 amino acids - organic compounds found in nature that combine to form proteins. Some amino acids are essential, meaning they need to be consumed. Other amino acids are non-essential because the body can make them.

Fats - 9 kcal per gram

Fats are triglycerides - three molecules of fatty acid combined with a molecule of the alcohol glycerol. Fatty acids are simple compounds (monomers) while triglycerides are complex molecules (polymers).

Fats are required in the diet for health as they serve many functions, including lubricating joints, helping organs produce hormones, assisting in absorption of certain vitamins, reducing inflammation, and preserving brain health.

Macronutrients that do not provide energy

These do not provide energy, but are still important:

Fiber

Fiber consists mostly of carbohydrates. However, because it is not easily absorbed by the body, not much of the sugars and starches get into the blood stream. Fiber is a crucial part of nutrition, health, and fuel for gut bacteria.

About 70 percent of the non-fat mass of the human body is water. It is vital for many processes in the human body.

Nobody is completely sure how much water the human body needs - claims vary from 1-7 liters per day to avoid dehydration. We do know that water requirements are very closely linked to body size, age, environmental temperatures, physical activity, different states of health, and dietary habits; for instance, somebody who consumes a lot of salt will require more water than another similar person.

Claims that 'the more water you drink, the healthier you are' are not backed with scientific evidence. The variables that influence water requirements are so vast that accurate advice on water intake would only be valid after evaluating each person individually.

Micronutrients

Micronutrients are required in smaller quantities:

Minerals

Minerals are found in a range of food types.

Dietary minerals are the other chemical elements our bodies need, other than carbon, hydrogen, oxygen, and nitrogen.

People with a well-balanced diet will, in most cases, obtain all the minerals they need from what they eat.

Minerals are sometimes added to certain foods to make up for any shortages.

The best example of this is iodized salt - iodine is added to prevent iodine deficiency, which affects about 2 billion people, globally; it causes mental retardation and thyroid gland problems. Iodine deficiency remains a serious public health problem in over half the planet.

Experts at the University of Florida say that 16 key minerals are essential for human biochemical processes:

Potassium

What it does - a systemic (affects entire body) electrolyte, essential in co-regulating ATP (an important carrier of energy in cells in the body, also key in making RNA) with sodium.

Deficiency - hypokalemia - can profoundly affect the nervous system and heart.

Excess - hyperkalemia - can also profoundly affect the nervous system and heart.

Chloride

What it does - key for producing stomach acid, important in the transport of molecules between cells, and vital for the proper functioning of nerves.

What it does - vital part of three important enzyme systems, xanthine oxidase, aldehyde oxidase, and sulfite oxidase. It has a vital role in uric acid formation, in carbohydrate metabolism, and sulfite detoxification.

Deficiency - may affect metabolism and blood counts, but as this deficiency often occurs at the same time as other mineral deficiencies, it is hard to say which deficiency caused which health problem.

Excess - there is very little data on toxicity.

Vitamins

Our bodies cannot synthesize vitamins, so we must consume them.

These are organic compounds we require in tiny amounts.

An organic compound is any molecule that contains carbon.

It is called a vitamin when our bodies cannot synthesize (produce) enough or any of it, so we need to get it from our food.

Vitamins are classified as water soluble (they can be dissolved in water) or fat soluble (they can be dissolved in fat). For humans, there are four fat-soluble vitamins (A, D, E, and K) and nine water-soluble vitamins (eight B vitamins and vitamin C).

Water-soluble vitamins need to be consumed more regularly because they are eliminated faster (in urine) and are not easily stored.

Fat-soluble vitamins are absorbed through the intestines with the help of fats (lipids). They are more likely to accumulate in the body because they are harder to get rid of quickly. If too many vitamins build up, it is called hypervitaminosis. A very low-fat diet can affect the absorption of fat-soluble vitamins.

We know that most vitamins have many different functions. Below is a list of vitamins, and some of their roles. Note that most often vitamin overdose symptoms are related to supplementation or impaired metabolism or excretion, not vitamin intake from foods.

Vitamin A

Chemical names - retinol, retinoids, and carotenoids.

Solubility - fat.

Deficiency disease - Night-blindness.

Overdose disease - Keratomalacia (degeneration of the cornea).

Vitamin B1

Chemical name - thiamine.

Solubility - water.

Deficiency disease - beriberi, Wernicke-Korsakoff syndrome.

Overdose disease - rare hypersensitive reactions resembling anaphylactic shock when an overdose is due to injection.

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